Selective fuel control for turbojet power plants



Aug. 25, 1 953 P. c. MANGAN ETAL SELECTIVEFUEL CONTROL FOR TURBOJET POWER PLANTS Filed March 10, i 1950 mm MM N .2223 FEE... R A 0 r0 m M Wm E V m 0 L U D ATTORNEY Patented Aug. 25, 1953 SELECTIVEFUEL CONTROL FOR TURBOJ-ET 7 POWER PLANTS Paul C'. Mangan, Ridley Park, and Robert A. Neal, Media, Pm, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania.

Application March 10, 1950, Serial No. 148,844

4 Claims.

This invention relates to, fluid fuel control apparatus, and more particularly to an aviation fuel system having selective primary and emergency control.

It has been proposed to equip a high-speed aircraft power plant, such as a gas turbine engine having. critical fuel requirements, with alternatively operative primary and stand-by or emergency fuel control means, for minimizing the dangerous. consequences of sudden failure of the fuel supply during flight. operation. Preferably, such a dual fuel control includes. primary and emergency pumps and is provided with means automatically operative to effect quick changeover from primary fuel control to emergency fuel control in the event of failure of the primary pump or other elements. associated therewith. It is an object of the present invention to provide improved fuel control apparatus. of this type, which isselectivel'y operative to render the emergency fuel control. quickly available under various flight operational conditions.

Another object of the invention is the provision of. improved. change-over or selector means for the dual fuel system of an aircraft power plant, wherein a selected operativepressure incident to normal. operation ofv the primary fuel control portion, during a take-oil operation for example, is rendered the determinative or measure of subsequent. performance thereof, so that a sudden reduction in efliciency of the primary system will be immediately detected to facilitate automatic change-over to the. emergency fuel control.

A further objectof the invention is to. provide improved aircraft. fuel control selector. means for elfecting change-over. from primary fuel. control to emergency fueljcontrol. which can be rendered quickly operative either automatically, as in' response to failure of the primary control to, maintain a predetermined performance level, or manually at the will of the pilot.

These and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming part of this application, in which. the single figure is a diagrammatic view of a dual fuel supply system for a power. plant of the gas turbine type, including emergency control and selector means therefor constructed in accordance with the invention.

In the drawing, a gas turbine engine Ill is provided, comprising a generally cylindricalcasing ll having axially mounted. therein a sectional core structure 12 an annular flui'dfiow passageway [3, which extends longitudinally through the engine from a forwardly-directed air intake opening [4 to a rearwardly disposed jet discharge nozzle 15. The operating components of the engine are arranged along the axis thereof and include an axial flow compressor [6, annular combustion apparatus I? and a turbine It, the rotor of which is operatively connected to the rotor of the compressor by a shaft Hi. In operation, with the engine disposed in an aircraft so that the air intake I4 is pointed in the line of flight, air entering the intake opening is compressed by the compressor l6 and passes through the passage [3 to the combustion apparatus IT for supportingcombustion of fuel,.which is supplied thereto in a manner hereinafter explained. The resultant hot motive fluid is then expanded through the turbine l 8 and discharged to atmosphere through the nozzle 15 in the form of a jet establishing a propulsive thrust.

For supplying fuel under suitable pressure to the combustion apparatus of the engine [0 there is provided a dual fuel control system, comprising a low pressure source of liquid fuel such as a tank and pipe system generally indicated at 2|, primary fuel control apparatus 22 having a primary pump 23, and stand-by or emergency fuel control apparatus generally indicated at 24 and having an emergency pump 25. Both pumps 23 and 25 are operatively connected through the medium of suitable shaft and gear mechanism 26 to the rotor of theengine compressor IE5, and are thus adapted to be driven simultaneously by the engine. Either the primary or the emergency fuel control apparatus 22 and 24' may be conditioned to control the metering of. fuel to the engine combustion apparatus I? through a pipe 28, the emergency control apparatus 24 being normally rendered inoperative, however, until failure or loss of efiici-ency of the primary control apparatus 22 renders necessary a change-over to fuel metering by the emergency control apparatus, as hereinafter more fully explained.

To simplify the present disclosure of the invention, the primary fuel control apparatus 22 is illustrated only in diagrammatic form without details other than the. primary pump 23. It will be understood that suitable features of construction and operation. may be embodied in the primary fuel control, such as means responsive to throttle position and engine speed for governing the flow of fuel to the combustion apparatus in accordance with operating conditions. By way of example, one suitable type of. primary control is. disclosed in the applicationv of. Cyrus F. Wood,

3 Serial No. 121,171, filed October 13, 1949, which has been assigned to the assignee of the present application. It will here suffice to point out that the primary pump 23 has an inlet connected to the tank or low pressure fuel source 2| and a discharge outlet communication 3| leading to the primary fuel control apparatus 22, the fuel discharge or metering communication 32 of which is connected to the pipe 28 leading to the combustion apparatus ll. A check Valve 33 is preferably interposed in the metering communication 32 for preventing back flow from the pipe 28.

The emergency fuel control apparatus 24 may be of any suitable construction operable to effect metering of fuel to the engine under sufficient control to enable uninterrupted operation thereof when the primary fuel control fails or is cut out of operation. In association with the emergency pump 25, the emergency control apparatus 24, as illustrated in the drawing, may comprise a filter 35, a manual throttle valve device 36, a differential relief valve 31, a barometric relief valve device 38 and a shut-down valve device 39, which are interposed in series relation in a pump discharge communication generally indicated at 45 and 45a, through which fuel discharged from the emergency pump 25 flows to the pipe 28 by way of a discharge communication 4| containing a check valve 22. An excesspressure responsive relief valve device 43 of conventional design may be provided for by-passing fuel from the pump discharge communication 43 to the low pressure source or pipe 2| in the possible event of building up of a fuel pressure high enough to jeopardize the operating elements of the fuel system.

The differential relief valve device 31 comprises casing structure containing a valve element 45 controlling another by-pass communication from the pump discharge communication 30 to the low pressure pipe 2|. The valve element A is actuated by a diaphragm 46 subject to opposing pressures of fuel at the inlet and discharge sides of the throttle valve device 36. A spring ll is provided for biasing the valve element 45 toward closed position, in opposition to pressure of fuel on the upstream side of the throttle valve device 33. In operation, the differential relief valve device 37 is adapted to bypass fuel under pressure from the pump discharge pipe lta to the low pressure pipe 2| in sumcient quantity to maintain a constant pressure drop across the throttle valve device 36, regardless of variations in fuel flow under different operating conditions. The throttle valve device 36 is preferably operative to control communication from the pump discharge All to either the communication 45311, or when shut off, to a branch 2 I a of the low pressure or inlet communication 2|.

The barometric relief valve device 38 is arranged to control the flow of fuel conducted through the communication 481a from the manual throttle valve device 36 in such a manner as to maintain a fixed pressure relationship under varying conditions of altitude, flight speed and ambient temperature, The device 38 comprises casing structure having a valve chamber 50 adapted to communicate with the pump discharge communication dlla, and an outlet chamber 5| which is interposed between the pump discharge communication 49a and communication 4|. A relief valve element 52 is mounted on one end of the valve chamber 50 for controlling communication therefrom to the low pressure pipe 2|, subject to operation of a diaphragm 53 that is connected thereto and interposed between chambers 50 and 5|. A light spring 55 may be associated with the diaphragm 53 for biasing the valve element 52 toward its seat in opposition to fuel pressure in the valve chamber 50. The valve element 52 is operative to maintain a fixed pressure relationship in cooperation with a flow divider valve element 51 having opposed seating portions, which is interposed between the connected portions of chambers 50 and 5| and actuated by a partially evacuated bellows diaphragm 55, subject to compressor inlet total and static air pressure admitted through a pair of conduits 6|, for dividing the flow of fuel under pressure from the manual throttle valve device 36 to the respective chambers 50 and 5| in accordance with changes in ambient pressure to maintain the engine rotational speed constant relative to throttle setting.

The shut-down valve device 39 serves to cut off all flow of fuel from the emergency control apparatus to the engine when the throttle is set in the shut-down position, or when the emergency control apparatus is inoperative, and comprises a valve element 65 having a stem 66 connected to a piston 61, which is mounted in casing structure between a chamber 10 communicating through a passage 69 with the low pressure pipe 2|, and a chamber 68 communicating with the emergency pump discharge communication 40. A spring H disposed in the chamber in acts on the piston 61 to urge the valve element 65 toward its seated position. The spring is thus operative to close the shut-down valve device 39 so long as the pressure of fuel in the pump discharge communication 40 is below a predetermined operational value. For indicating to the pilot that the engine is operating on the emergency system when such is the case, an electro-responsive cockpit indicator 13 may be provided, to be energized through a suitable circuit 14 upon operation of a switch '15 by a stem 16 of the piston 61 when the latter is moved by emergency fuel pressure against the force of the spring II.

It will be understood that the elements of the emergency fuel control apparatus 24, just de scribed, may in practice be constructed and arranged in a unitary casing structure having suitable passages for affording the desired communications.

According to the invention, for selecting operation of either the primary fuel control apparatus 22 or the emergency fuel control apparatus 24, while rendering inoperative whichever apparatus is not to function, there are provided a change-over or selector valve device 80, and a pilot valve device 8| for effecting quick operation thereof in the event of failure of the primary control during a take-off operation of the aircraft.

The selector valve device comprises a casing 83 having a bore in which a piston valve element 84 is slidably mounted, forming on one side a control chamber 85 which communicates with the primary pump discharge communication 3| by way of one branch of a communication 86 including a check valve 81 for preventing backflow to the communication 3|. A restricted passage 88 may be provided upstream of the check valve 81 for minimizing surging of pressure in the control chamber 85. Disposed on the opposite side of the piston valve element 84 is a biasing spring 90, which is adapted to urge the valve element toward its emergency position. upon.v predetermined. reduction. in; fuel. pressure. in the. chamber 8.5; ashereinatter explained. With the piston valve element 814 maintained. in. its normal positiomas shown in: the drawingacavity 91 therein registers with. a. port-92. connected to. the emergency pump dischargecommunication 40;. and with a. port. 93 which. is connected, to. the low pressure. pipe system. 2|. Eur. ensurin initial movement of the pistonvalve. element. 81 to. normal position. in. oppositionto the force of; spring 90 when the fuel supply apparatus. is started,.a branchcommunication. and. check. valve. 9.4. are provided to conduct. fuel from. the emergency pump discharge communication. 41! through. the communication 86 to. the. control chamber. 8.5, augmenting. the. output of primary pump. 23-

Associated with. the selector valve. device 80' is afuelpressure responsive. pilot or release valve device 95, comprising. a. casinghaying. a bore in which apiston valve element 9.3. is. subjected to the. force of a. spring. 99a and adapted for movement thereby for establishing. communication I from the control. chamber. 8% to'thelow pressure.

pipe. 2t by way of a communication. 91'. The valve element 96 isnormally maintained in a closed positioru asshown, by. the pressure offjuel in. achamber 98. communicating, with. the.v primary pump. discharge communication 3]..

A normally closed electro-responsive release valve device- L is. alsointerposed between the communications 91 and. 21,. and is. adapted to be actuated: to.- establish communication therebetween upon energizationo-fa circuit Ill Lincluding an operating. magnet H12, which circuit. is. preferably' controlled. manually. through the medium ot a suitable switch lfl3-..

The; pilot. valve device. 81: comprisescasing sections I05 and. Lilli having clamped therebetween a flexible diaphragm M1,. which has formed on oneside thereof. aspring chamber. ")8 communieating. with a conduit [09 which. is. at. all. times in communication. with the. outlet. communication 32 of the primary control apparatusZL.

On the other side-of the diaphragm. [.07. is provided. an. expansible accumulator chamber l !0, which has a bellows diaphragm. or. yieldable. wall tlll- (shown. diagrammatically). and isconnected to-theconduit Hi9 throughthe medium of anormally open electr c-responsive.cuteofi valve device 0 H2: including an actuating magnet Ilia. The latter is adapted; to be energized, for cutting off communication between chamber H0 and conduit N39,; by means of a suitable" circuit H3: con.- trolled by. amanual. switch ll.4-. Afollower and plunger l l'i', terminating ina valve I'l"! interposed in communication 91, are mounted in operative connection with the diaphragm. L01, which is thus constructed and. arranged: to; respond to a reduction. in fluid pressure in spring chamber I08 to move the valve H1 for establishing communication fromthe control chamber 85 of the selector valve device to the low pressure communication 2l. A coil spring H8 is interposed between the follower of the diaphragm I01 and a Wall of spring chamber I08 for normally maintaining the valve II! in its closed position, as shown in the drawing.

To describe operation of the invention it will be assumed that the aircraft equipped with the power plant and fuel system. hereinbefore described is about to take off, with the primary pump 23 and control apparatus 22 operated to deliver fuel to the combustion apparatus I! at a high rate of flow to ensure development of adevalve ll'lf to. its open position. With fuel, under operation. cuit. H3 isenergizedj to effect. closure of the. cutofi'valye device. HZ, bottling up inv the, accumuquatethrust... The pressure of" fuel: in the.primarry pump. discharge communication lg andconsequently irrthe cont'rolichamber 85' is thenhigh enough. to maintain. tlie piston valve element 84 its. normal position. as, illustrated;. while the fueldischargedLby. the emergency pump is circulatedl through. the. communication 40.; and through, the. connectediports. 92, 91". and 93 to the low pressure; fuel" source 21., thus maintaining. the

emergency controliapparatus 24 in an inoperative condition. If. the pilot. at. such time desires. the protectionof the. automatic safety feature provided. by. the accumulator pilotv valve device 81,

hewill. close. the switch, H4 while. the power. plant developing thrust incident tothe take-off With the. switch 114- closed, the cirand. I09. and in chamber. L08, will. cause quick response of the diaphragm UH under pressure of the entrapped fuel; in chamber Illl' to. overcome the. force of. spring, H8, for shifting the pressure. thus quickly released: from the control chamber $15; the. spring. 93 will be rendered effective. to. move. the valve elementv 8.4 to

emergency position. In this. position of the piston valve element, the. cavity 9.! connects a port Ill). to the port. 93,.thereby causing. by-pass flow to the low pressure. pipe, 2] of any fuel' subsequentl'y discharged. from the primary pump 23. At. the. same. time. further by-passing. of fuel from the emergency pump. 25 by way of the selector. valve device. '80 is cutoff; and the emergency. fuel control apparatus 24 is thus. rendered operative to assume. the burden of metering fuel under pressure tothe. engine H1 in the manner. already explained.

After completion of a. protected take-01f. operation. of the. aircraft under ordinary circumstances whichhave. not involved. a failure of the primary fuel. control. apparatus, the pilot may restore the dual. fuel. system to normal flight conditionby, returning the switch Hi l to its normalopenposition.

The. pilot may at any time render the emergency fuel control apparatus 24 operative, independently .of possible. functioning of the automatic. pilot. valve. device. 3 l.,. by closing, switch 7 [503. to effect opening. of the release valve device 1100.. In case. of. an. electrical. power failure, the fluid pressureresponsive release valve device Q5 will. ultimately operate in. response to predeterminedreduction; in pressure of fuel from the aceaeos receive fuel at variable primary system pressure, a biasing spring, a movable control element operable against the force of said spring to effect a change-over operation, a movable abutment operatively connected to said control element, a control chamber communicating with the primary fuel supply passage, an expansible accumulator chamber also communicating with said primary fuel passage, said movable abutment being interposed between said control and accumulator chambers, and a valve for cutting off the communication between said primary fuel passage and said accumulator chamber for bottling up fuel therein at a selected primary system pressure, said movable abutment being thereafter operable by pressure of fuel in said accumulator chamber to operate said control ele ment upon a relative reduction in control chamber pressure indicative of failure of said primary fuel system.

2. In a liquid fuel system for a power plant,

in combination, a low pressure fuel source, primary and emergency pumps connected to the fuel source, primary control means having an outlet and normally operative to control the supply of fuel under pressure from said primary pump by way of said outlet, emergency control means having an outlet and operable to control the supply of fuel under pressure thereto from said emergency pump when said primary means is rendered inoperative, a fluid pressure responsive selector valve device having one position for opening a first by-pass communication between the outlet of said primary pump and said fuel source and another position for opening a second by-pass communication between the outlet of said emergency pump and said fuel source, said selector valve device having a control cham ber connected to said outlet of said primary pump for subjecting said selector valve device to primary fuel pressure for normally maintaining said selector valve device in the position in which only said second by-pass communication is opened, a normally closed pilot valve interposed in a discharge communication between said control chamber and said low pressure fuel,

source, and fiuid pressure means connected to the outlet of said primary control means for actuating said pilot valve in response to a predetermined reduction in pressure of fuel delivered by said primary control means, whereby said selector valve device is actuated to close the second by-pass communication forrendering said emergency control means thereafter eifective to control the supply of fuel from said emergency pump.

3. In a fuel pressure system, a low pressure fuel source, primary control means including a primary pump and having a fuel pressure outlet, said primary control means being operative for normally regulating the supplying of fuel under pressure by said pump to a power plant, emergency control means including an emergency pump and operative for regulating the supplymeans, a first bypass adapted to connect together the discharge outlet and the inlet of said emergency pump, a second bypass for connecting to gether the discharge outlet and inlet of said primary pump, a fuel pressure responsive selector valve device operative to open either of said bypasses while closing the other and having a control chamber normally charged at primary pump pressure, said selector valve device normally holding open said first bypass and being operative to close the latter while opening said second bypass upon reduction in primary fuel pressure in said control chamber, and consequently to out said emergency control means into operation, an accumulator pilot valve device comprising a discharge valve controlling communication between said control chamber and the low pressure fuel source, a fixed volume chamber and an expansible accumulator chamber communicating with the fuel pressure outlet of said primary control means, a movable abutment interposed between said fixed volume and accumulator chambers for actuating said discharge valve, and a cut-off valve interposed in the communication between said fuel pressure outlet and said expansible accumulator chamber, said cut-off valve being operable at will to bottle up said fuel in said accumulator chamber at the pressure attained during a full power output stage of operation of said primary control means, for subsequently effecting operation of said abutment and discharge valve to release fuel from said control chamber, thereby effecting operation of said selector valve device for rendering operative said emergency control means, in the event of failure of said primary control means to maintain substantially the same pressure in said fixed volume chamber as initially provided in said accumulator chamber.

4. Fuel control selector apparatus as set forth in claim 3 having in combination, a normally closed release valve interposed in a communication between the control chamber and the low pressure source in parallel with said communication controlled by the discharge valve of the accumulator pilot valve device, said release valve being manually operable for effecting operation of the selector valve to render the emergency control system operative regardless of the condition of the primary control system.

PAUL C. MANGAN. ROBERT A. NEAL.

References Cited in the file of this patent UNITED STATES PA'IENTS Number Name Date 2,440,371 Holley Apr. 2?, 194a FOREIGN PATENTS Number Country Date 918,123 France Oct. 7, 1946 

